[imp] From address using vmailmgr virt user

[Abu]

I setup qmail+vmailmgr and imp as webmail, 
and try to change maildomain='sample.com' in servers config,
then login as virtual user like:

    login: a at sub.sample.com
    pass: xxx

but when i send email the from: stil using virt domain, a at sub.sample.com,
rather a at sample.com

there is something i missing?

-az